I've done it. Here is my divided tank.
Its 100L (26g) divided into 4 sections. One section is half the tank (about 13g) with 3 juvenile females and the other sections are just over 4 gallons each with a crowntail male in each. They can see each other through the dividers. One male and the females can see each other. So far it's been 2-3 weeks with the males and 1 week with the females and everything is going great. Very early days yet. I can tell you the males flared at each other for the first week but there was no attacking dividers or pacing back and forth. No stressing. They now ignore each other completely. They know each section is their own and the other bettas are in theirs. The females occasionally look through the divider at the male they can see but neither have ever flared or stressed over each other.
(I do have back up plans and this was thought through thoroughly)